How to implement file upload and processing in FastAPI

How to implement file uploading and processing in FastAPI

FastAPI is a modern, high-performance web framework that is easy to use and powerful. It provides native support for file uploading and processing. In this article, we will learn how to implement file upload and processing functions in the FastAPI framework, and provide code examples to illustrate specific implementation steps.

First, we need to import the required libraries and modules:

from fastapi import FastAPI, UploadFile, File
from fastapi.responses import JSONResponse
import shutil
import os

Next, we need to create a FastAPI application instance:

app = FastAPI()

Now, we can define a route to Accept the file upload request and save the file to the server:

@app.post("/upload/")
async def create_upload_file(file: UploadFile = File(...)):
    try:
        # 保存文件到服务器上
        with open(file.filename, "wb") as buffer:
            shutil.copyfileobj(file.file, buffer)
        
        # 返回成功的响应
        return JSONResponse({"message": "File uploaded successfully"})
    except Exception as e:
        # 返回失败的响应
        return JSONResponse({"error": str(e)}, status_code=500)

In the above code, we define a POST request route /upload/, which Receive a parameter named file, the type of the parameter is UploadFile, we use the File function to parse it as a file in the request body. File The first parameter of the function is the default value of the file type, ... means that this parameter must be passed, otherwise an error response will be returned.

When processing a file upload request, we first use with open to create a file writing stream, and then use the shutil.copyfileobj function to put the request body into The file object is copied to the server.

When the file is uploaded successfully, we return a JSON response containing a success message; if any exception occurs during the file upload, we will return a JSON response containing error information and set the response status code to 500.

After the file upload function has been implemented, we can continue to implement the file processing function. The following is an example route that accepts uploaded image files and converts the image files into thumbnails:

@app.post("/process_image/")
async def process_image(file: UploadFile = File(...)):
    try:
        # 保存文件到服务器上
        with open(file.filename, "wb") as buffer:
            shutil.copyfileobj(file.file, buffer)
        
        # 进行图片处理，生成缩略图
        thumbnail_filename = f"thumbnail_{file.filename}"
        # 模拟图片处理过程
        # 请根据实际需求进行实现
        # ...
        
        # 返回缩略图的下载链接
        return JSONResponse({"thumbnail_url": f"/download/{thumbnail_filename}"})
    except Exception as e:
        # 返回失败的响应
        return JSONResponse({"error": str(e)}, status_code=500)

In the above example code, we used the same file upload process and then moved into image processing logic. Here, we use simulation to process image files, generate thumbnails, and return the thumbnail download link to the client.

Finally, we can also define a route to provide the download function:

@app.get("/download/{filename}")
async def download_file(filename: str):
    try:
        # 返回文件下载链接
        return JSONResponse({"download_url": f"/file/{filename}"})
        
    except Exception as e:
        # 返回失败的响应
        return JSONResponse({"error": str(e)}, status_code=500)

In the above code, we define a GET request route/download /{filename}, this route accepts a file name parameter filename and returns the download link of the file.

At this point, we have implemented the function of file upload and processing in the FastAPI framework. Through the above sample code, we can understand the basic process of handling file upload and processing in FastAPI, and how to use FastAPID's API and methods to implement these functions. Of course, the specific file processing logic can be customized according to actual needs.

I hope this article will help you understand how to implement file upload and processing functions in FastAPI!

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